1. Field of the Invention
The invention generally relates to alleviating barred access and, more particularly, to an apparatus, such as a user equipment or a chipset for the user equipment, and a method for a radio resource control (RRC) protocol to alleviate barred access while reselecting from a first cell to a second cell in a mobile communication system.
2. Description of the Related Art
The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
In a typical cellular radio system, a mobile user equipment (UE) communicates via a radio access radio network (RAN) to one or more core networks. A UE comprises various types of equipment such as a mobile telephone (also known as cellular or cell phone), a laptop with wireless communications capability, a personal digital assistant (PDA) etc. These may be portable, handheld, pocket-sized, installed in a vehicle etc. and communicate voice and/or data signals with the radio access network.
The radio access network covers a geographical area divided into a plurality of cell areas. Each cell area is served by at least one base station, which may be referred to as a Node B. Each cell is identified by a unique identifier which is broadcast in the cell. The base stations communicate at radio frequencies over an air interface with the UEs within the range of the base station. Several base stations may be connected to a radio network controller (RNC) which controls various activities of the base stations. The radio network controllers are typically connected to a core network.
A universal mobile telecommunications system (UMTS) is a third generation mobile communication system that has evolved from the Global System for Mobile communications (GSM) system. The UMTS is a European standard which aims to provide better mobile communication services based on the GSM core network and wideband code division multiple access (W-CDMA) technology. While UMTS delivers high data transfer rates, wireless data usage is expected to increase significantly over the next few years. For this reason, concepts for UMTS Long Term Evolution (LTE) have been proposed and the objective is to further improve UMTS to achieve high-data-rates, low-latency and packet-optimized radio access technology. The improved UMTS is called Evolved Universal Terrestrial Radio Access (E-UTRA).
For a wireless mobile device, generally referred to as a UE, which complies with a 3GPP specification for an E-UTRA protocol, the 3GPP TS 36.331 specification, v.8.3.0, referred to herein as the 36.331 specification, defines the E-UTRAN RRC (Radio Resource Control) protocol requirements between the E-UTRA Terrestrial Radio Access Network (E-UTRAN) and the UE. The 3GPP TS 36.304 specification, v.8.3.0, referred to herein as the 36.304 specification, defines the E-UTRAN RRC protocol requirements for the UE in an idle mode.
Clause 8.1.1 of the 36.331 specification, relates to the broadcast of system information. The E-UTRAN sends system information to a UE by means of a message that comprises a Master Information Block (MIB) and a plurality of System Information Blocks (SIBs), as illustrated in FIG. 1. The MIB provides references and scheduling information for a number of system information blocks. A system information block groups together system information elements of the same nature. Different system information blocks may have different characteristics, e.g. repetition rates and the requirements on UEs to re-read system information blocks. The system information blocks contain the actual system information. The master information block may optionally also contain reference and scheduling information of one or two scheduling blocks, which give references and scheduling information for additional system information blocks. Scheduling information for a system information block is included in either the master information block or one of the scheduling blocks.
In accordance with clause 5.3.7.2 of the 36.331 specification and clause 5.2 of the 36.304 specification, before a UMTS cell is selected by a mobile device, the system information of the cell, including MIB and SIBs, is read on the broadcast control channel (BCCH). Together with the detected signal strength of the cell, a UE can then determine whether a cell is qualified to be camped on or not. After the UE selects the cell and camps on it, in accordance with clause 5.3.3.2 of the 36.331 specification, the UE determines whether access to the E-UTRAN is allowed or not by the system information before the UE can initiate a connection establishment procedure. The access control categories are defined in three service types by the system information as “mobile terminating access”, “mobile originating calls”, and “mobile originating signaling”. If the access of a service is barred, the RRC protocol of the UE starts a corresponding barred access timer and before the barred access timer expires, the corresponding access is prohibited. When the barred access timer expires, the RRC protocol of the UE informs the upper layers that the access is granted, so that the UE can then initiate the connection establishment procedure.